I. Field of the Invention
This invention relates generally to an apparatus and method for performing percutaneous transluminal angioplasty and more particularly to an improved catheter arrangement for allowing simultaneous dilatation of the lesion being treated and the administration of an appropriate drug or other liquid substance at the treatment site.
II. Discussion of the Prior Art
Prior to the mid-1970's, the principal method of treating atheromas or other stenotic lesions in a blood vessel was to surgically excise the blockage or, in the case of coronary arteries, bypass the plugged arteries with a graft usually harvested from the patient's leg. More recently, and following a procedure first advanced by Dr. A. Gruenzig, a balloon catheter is introduced at an appropriate location and routed through the vascular system to the site of the lesion to be treated. With the balloon juxtaposed relative to the blockage or constriction, an inflation fluid is introduced through the lumen of the catheter and made to inflate the balloon to expand same against the blockage and to spread or open the obstructed blood vessel. Such a procedure is far less traumatic than prior surgical procedures.
The patent literature contains an appreciable number of patents pertaining improvements in dilatation catheter structures. Generally speaking, they address improvements in materials employed, torquing characteristics, and, of course, size reduction so that relatively small blood vessels can be treated. A problem still remains with the percutaneous transluminal coronary angioplasty (PTCA) procedure in that the treated blood vessel sometimes does not remain patent. In fact, and perhaps 33 percent of the cases, within 12 months it is necessary to repeat the procedure. It has long been known that certain drugs are effective in reducing the reformation of certain types of stenotic lesions. For example, there are drugs under evaluation which show a tendency to inhibit smooth muscle cell growth. Because of the nature of this drug, it is not desirable that it be injected as a bolus dose and merely be allowed to be carried by the blood stream to the situs of the lesion. This is because in the dosage which would be required, that drug can have undesirable side effects. However, and in accordance with the present invention, if that drug can be administered directly to the lesion, a significantly smaller dosage may be employed and the side effects minimized.
It has also been suggested that following the angioplasty or atherectomy procedure that a mechanical stent be inserted and positioned at the treatment site to inhibit restenosis. However, to date no effective way, other than a direct surgical access, has been devised for positioning the stent. Because in the case of coronary artery repair rather traumatic surgery is required, the advantages of balloon angioplasty are wasted.